Medium density fiberboard, or MDF, is a composite wood product similar to particleboard. It's made out of wood waste fibers glued together with resin, heat, and pressure. MDF is appropriate for many applications, from cabinetry to moulding, because it is smooth, uniform, and won't warp.

MDF has many advantages over plank wood, particleboard, or high density fiberboard. It's very smooth because the wood fibers used in its manufacture are uniform and fine. This makes it have low "tear out," which means that when sawed, the end has a smooth cut instead of a jagged edge. This also means that a coat of primer and a couple of coats of paint take well, leaving an attractive, finished surface unlike other composite wood products. MDF also has a mild reaction to moisture, meaning it won't warp or swell in high-humidity applications like a bathroom cabinet.

Builders use MDF in many capacities, such as in furniture, shelving, laminate flooring, decorative moulding, and doors. They value MDF for its insular qualities in sound and heat. Also, it can be nailed, glued, screwed, stapled, or attached with dowels, making it as versatile as plank wood. Usually, people working with MDF use a carbide saw fitted with a vacuum to reduce the amount of airborne dust. Since MDF is strengthened with resin containing formaldehyde, those at exposure try to reduce their risk of inhalation, or use special MDF with lower formaldehyde levels.

Reconstituted, engineered wood products like MDF are often covered in a veneer or laminate. These thin layers of vinyl or real wood disguise the MDF, especially along visible edges. Some people prefer using MDF over regular lumber because it has a lower impact on the environment. MDF is solely made from waste products, the leftover scraps that would otherwise be dumped in a landfill. This attraction has helped it gain popularity among homeowners. It's now available not just to contractors. Many home improvement centers and lumberyards stock it in sheets for the general public.